The Lapitxuri experimental site

Scientific and technical context

In 1980, INRA built the Lapitxuri experimental site, organized around a large, semi-natural channel. The initial purpose was to study the optimum conditions for the growth of Atlantic salmon and to define the scientific bases for the production of juveniles to supplement salmon populations. Since its creation, scientific questioning have evolved and many collaborative scientific programs have used the site for experiments in ecology and behavioral studies (growth, dispersion, reproduction). The site is most original and is one of a kind in Europe.

Facilities

The INRA Lapitxuri experimental site was settled on the upstream area of the Nivelle basin, in the vicinity of Aïnhoa village. The absence of intensive agriculture and other human activities ensure the high physical and chemical quality of the water and the absence of pollution. Average temperatures vary between 4 and 20° C over the course of a year. The site is recognized to be free of SHV/NHI (approval number 64330056) and is monitored yearly by the Aquitaine GDSA and the DSV 64.

The facility is made of four components:

Semi-natural channel: it is fed by a deviation of the Lapitxuri brook. It is 130 m long with a 2% slope and is composed of a succession of 13 sections, 10 m x 2.8 m each. The incoming flow of water can be adjusted from 50 to 150 liters per second, and an automatic pumping and recirculation system delivers water back to the top of the channel to compensate for eventual shortages of incoming water flow. The granulometry (10 to 80mm) and the physical parameters (water depth, area and connections between courses, etc.) can also be adjusted. Bird netting prevents predation on the fish. One of the channel's original features is the possibility of observing behavior from underwater viewports or with video cameras. At night, external infra-red lighting also allows some behavioral observations.

Eight small channels (10m x 0.5, depth: 0.25m): they allow experiments on young fish (size<10 cm). Various sets of meshed walls or upstream or downstream fish traps can also be installed. Shade netting prevent the water from heating, the growth of algaes and bird predation. The water feeding the channels is filtered down to 15 µm and the maximum flow is 52 liters per second. They are equiped with a passive security system that prevents interruptions in water supply in case of power failures.

Hatchery: it allows the incubation and monitoring of small batches of eggs and alevins. It is equiped with two Heath-type incubators (with a capacity of 160,000 eggs), six incubation troughs and six 60 L tanks. The water supply is filtered down to 15 µm to prevent the incubation “clayettes” from being plugged in the event of flooding.

Growth platform: it consists of 16 Swedish-style 4m² ponds and 8 additionnal 1m² ponds. It allows fish to be held temporarily and to raise juveniles as part of on-site or off-site.

Applications

The semi-natural channel mimics the living conditions of salmonids in their wild environment. It has, for example, allowed studies on: - behavioral interactions between juvenile salmonids - sexual selection in trout and salmon - natural hybridation between trout and salmon - the impact of clogging on embryo-larval survival rates

More recently, studies have focused on the impact of climate change (and notably flow) on fish growth, life history (early sexual maturation) and spawning (sexual selection).